Ole Hertel

Personal exposure to ultrafine particles and oxidative DNA damage.

Exposure to ultrafine particles (UFPs) from vehicle exhaust has been related to risk of cardiovascular and pulmonary disease and cancer, even though exposure assessment is difficult. We studied personal exposure in terms of number concentrations of UFPs in the breathing zone, using portable instruments in six 18-hr periods in 15 healthy nonsmoking subjects. Exposure contrasts of outdoor pollution were achieved by bicycling in traffic for 5 days and in the laboratory for 1 day. Oxidative DNA damage was assessed as strand breaks and oxidized purines in mononuclear cells isolated from venous blood the morning after exposure measurement. Cumulated outdoor and cumulated indoor exposures to UFPs each were independent significant predictors of the level of purine oxidation in DNA but not of strand breaks. Ambient air concentrations of particulate matter with an aero-dynamic diameter of ≤10 μm (PM10), nitrous oxide, nitrogen dioxide, carbon monoxide, and/or number concentration of UFPs at urban background or busy street monitoring stations was not a significant predictor of DNA damage, although personal UFP exposure was correlated with urban background concentrations of CO and NO2, particularly during bicycling in traffic. The results indicate that biologic effects of UFPs occur at modest exposure, such as that occurring in traffic, which supports the relationship of UFPs and the adverse health effects of air pollution.

Test of two numerical schemes for use in atmospheric transport-chemistry models

Abstract Two fast integration methods for chemical kinetics are tested. One is the Quasi-steady State Approximation (QSSA) method and the other is a new Euler Backward Iterative (EBI) method. The EBI method is based on iterative solution of the Euler backward approximation of a coupled system of nonlinear ordinary differential equations of chemical kinetics. The efficiency of the iteration process is increased by using analytical solutions for groups of species which are strongly coupled. The accuracy of both integration methods is evaluated by comparing the results with solutions obtained by a Gear method, the Livermore Solver for Ordinary Differential Equations (LSODE). The chemical scheme used is the Carbon-bond Mechanism IV (CBM-IV). The numerical methods are tested of three chemical scenarios: two scenarios without emissions and with constant reaction rates and one scenario with variable emissions and photodissociation rates. Using a short time step (50 s), both EBI and QSSA perform very well, even under extreme chemical conditions. For larger time steps the EBI method performs better than QSSA. In the case of more realistic chemical conditions, both methods perform well even with a time step of 900 s. The accuracy of QSSA depends highly on the iteration procedure. Without iterations the QSSA method performs poorly. The great advantage of the EBI method is that concentrations are computed using linear operators only. Because of this, the method is mass conserving and can be used in air pollution transport models where higher moments of concentration distributions also need to be evaluated. Both the QSSA and the EBI methods can be recommended for use in atmospheric transport-chemistry models, where accuracy as well as computational efficiency is important. In general, the new EBI method is, however, more efficient than QSSA with a constant number of iterations.

Towards a climate-dependent paradigm of ammonia emission and deposition

Existing descriptions of bi-directional ammonia (NH3) land–atmosphere exchange incorporate temperature and moisture controls, and are beginning to be used in regional chemical transport models. However, such models have typically applied simpler emission factors to upscale the main NH3 emission terms. While this approach has successfully simulated the main spatial patterns on local to global scales, it fails to address the environment- and climate-dependence of emissions. To handle these issues, we outline the basis for a new modelling paradigm where both NH3 emissions and deposition are calculated online according to diurnal, seasonal and spatial differences in meteorology. We show how measurements reveal a strong, but complex pattern of climatic dependence, which is increasingly being characterized using ground-based NH3 monitoring and satellite observations, while advances in process-based modelling are illustrated for agricultural and natural sources, including a global application for seabird colonies. A future architecture for NH3 emission–deposition modelling is proposed that integrates the spatio-temporal interactions, and provides the necessary foundation to assess the consequences of climate change. Based on available measurements, a first empirical estimate suggests that 5°C warming would increase emissions by 42 per cent (28–67%). Together with increased anthropogenic activity, global NH3 emissions may increase from 65 (45–85) Tg N in 2008 to reach 132 (89–179) Tg by 2100.

Development and testing of a new variable scale air pollution model—ACDEP

A comprehensive trajectory model, Atmospheric Chemistry and Deposition model (ACDEP), has been developed to calculate the nitrogen deposition to the Danish sea waters. The model is constructed with the ability of taking into account spatially detailed emissions and land use data for Denmark and on a more coarse grid for the rest of Europe. In the ACDEP-model a one-dimensional column is advected along 96 h back-trajectories. The chemical mechanism in the model is a slightly extended version of the Carbon-Bond Mechanism IV (CBM-IV). The model describes the dry deposition processes with special emphasis on the conditions at sea. For the wet deposition processes both in-cloud and below-cloud scavenging are taken into account. The model results are tested versus one years measurements from six Danish and one Swedish monitoring station. Additional tests are performed for six selected stations from the European Monitoring and Evaluation Programme (EMEP) networks. The model is capable of reproducing both air concentrations and wet depositions of the nitrogen compounds in land and sea areas.

Using measurements of air pollution in streets for evaluation of urban air quality : meterological analysis and model calculations

Measurements of urban air pollution are usually confined to a few locations within a city area. Monitoring stations are often situated in streets with significant traffic levels or in places where severe pollution problems are expected. Such measurements are naturally influenced by very local conditions and care must be taken in interpreting the results. This is especially important when the measurements are used for estimating urban air pollution levels or comparing air quality in different cities. Another frequent application of street measurements is for public information or warning the population of elevated pollution levels. Estimating the dangers of long-term exposure to air pollution means careful consideration must be given to how representative these measurements actually are. In this paper the influence of local conditions on air pollution concentrations is discussed, regarding especially the dependency of pollution levels on street configuration and meteorolgical parameters. The examples used are based on measurements from locations in Copenhagen and on model calculations using the Danish Operational Street Pollution Model (OSPM). It is shown that large concentration gradients can occur in street canyons with leeward concentrations far higher than windward concentrations. Thus, street measurements are site-dependent and not representative for urban areas. Model calculations with OSPM agree well with measurements.

A DANISH DECISION-SUPPORT GIS TOOL FOR MANAGEMENT OF URBAN AIR QUALITY AND HUMAN EXPOSURES

Abstract A new prototype model system named AirGIS has been developed to support local authorities in air quality management for big Danish cities. The system is based on the Danish operational street pollution model (OSPM), technical and cadastral digital maps and Danish national administrative databases on buildings, cadastres and populations. It applies a geographic information system (GIS). AirGIS estimates ambient air pollution levels at high temporal and spatial resolutions. The model system enables mapping of traffic emissions, air quality levels and human exposures at residence addresses, at workplace addresses and in streets. Mapping and scenario results can be compared with air quality limits. Impact assessment of traffic air pollution abatement measures can also be carried out.

Transition metals in personal samples of PM2.5 and oxidative stress in human volunteers.

Ambient particulate matter (PM) has been associated with increased risk of lung cancer. One proposed mechanism is that PM induces oxidative stress mediated by transition metals contained within this mixture. We examined the relationship between the personal exposure to water-soluble transition metals in PM2.5 and oxidative DNA damage. In 49 students from central Copenhagen, we determined PM2.5 exposure by personal sampling twice in 1 year, and measured in these PM2.5 samples the concentration of the soluble transition metals vanadium, chromium, iron, nickel, copper, and platinum. Collected lymphocytes and 24-hour urine samples were analyzed for DNA damage in terms of 7-hydro-8-oxo-2′-deoxyguanosine (8-oxodG). We found that the 8-oxodG concentration in lymphocytes was significantly associated with the vanadium and chromium concentrations with a 1.9% increase in 8-oxodG per 1 μg/L increase in the vanadium concentration and a 2.2% increase in 8-oxodG per 1 μg/L increase in the chromium concentration. We have previously reported that in this study population the personal exposure to PM2.5 was associated with an increase in 8-oxodG in lymphocytes. However, vanadium and chromium were associated with the 8-oxodG concentration in lymphocytes independently of the PM2.5 mass concentration. The four other transition metals were not associated with 8-oxodG in lymphocytes and none of the transition metals was significantly associated with 8-oxodG in urine. Our results could indicate that vanadium and chromium present in PM2.5 have an effect on oxidative DNA damage that is independent of particle mass and/or other possible toxic compounds contained within this particulate mixture.

Actual car fleet emissions estimated from urban air quality measurements and street pollution models.

A method to determine emissions from the actual car fleet under realistic driving conditions has been developed. The method is based on air quality measurements, traffic counts and inverse application of street air quality models. Many pollutants are of importance for assessing the adverse impact of the air pollution, e.g. NO2, CO, lead, VOCs and particulate matter. Aromatic VOCs are of special great concern due to their adverse health effects. Measurements of benzene, toluene and xylenes were carried out in central Copenhagen since 1994. Significant correlation was observed between VOCs and CO concentrations, indicating that the petrol engine vehicles are the major sources of VOC air pollution in central Copenhagen. Hourly mean concentrations of benezene were observed to reach values of up to 20 ppb, what is critically high according to the WHOs recommendations. Based on inverse model calculation of dispersion of pollutants in street canyons, an average emission factor of benzene for the fleet of petrol fuelled vehicles was estimated to be 0.38 g/km in 1994 and 0.11 in 1997. This decrease was caused by the reduction of benzene content in Danish petrol since summer 1995 and increasing percentage of cars equipped with three-way catalysts. The emission factors for benzene for diesel-fuelled vehicles were low.

An air pollution model for use in epidemiological studies: evaluation with measured levels of nitrogen dioxide and benzene.

The aim of the study was to evaluate the predictions derived from the Danish Operational Street Pollution Model (OSPM) when the input data are obtained by simple methods that could be used in large-scale epidemiological studies. The model calculations were thus compared with passive sampler measurements of nitrogen dioxide and benzene at 103 street locations in Copenhagen, Denmark, and at 101 locations in rural areas. Data on traffic and street configuration were collected by means of a simple registration scheme in which forms were filled out by local municipal authorities. Meteorological data were derived from routine measurements at Copenhagen airport, and data on background air pollution were based on a simple empirical model. Differences in air pollution levels between rural areas and Copenhagen and differences in nitrogen dioxide concentrations at various locations in Copenhagen were well reproduced by the OSPM. The correlation coefficients (r) between the measured and the predicted half-year average concentrations of nitrogen dioxide in Copenhagen were between 0.75 and 0.80 for various degrees of precision of the input data for the model. The results indicate that the OSPM used with the presented methods for generation of input data might be useful in assessing long-term exposure to air pollutants in epidemiological studies.

Policies for agricultural nitrogen management—trends, challenges and prospects for improved efficiency in Denmark

With more than 60% of the land farmed, with vulnerable freshwater and marine environments, and with one of the most intensive, export-oriented livestock sectors in the world, the nitrogen (N) pollution pressure from Danish agriculture is severe. Consequently, a series of policy action plans have been implemented since the mid 1980s with significant effects on the surplus, efficiency and environmental loadings of N. This paper reviews the policies and actions taken and their ability to mitigate effects of reactive N (Nr) while maintaining agricultural production. In summary, the average N-surplus has been reduced from approximately 170 kg N ha?1 yr?1 to below 100 kg N ha?1 yr?1 during the past 30 yrs, while the overall N-efficiency for the agricultural sector (crop?+?livestock farming) has increased from around 20?30% to 40?45%, the N-leaching from the field root zone has been halved, and N losses to the aquatic and atmospheric environment have been significantly reduced. This has been achieved through a combination of approaches and measures (ranging from command and control legislation, over market-based regulation and governmental expenditure to information and voluntary action), with specific measures addressing the whole N cascade, in order to improve the quality of ground- and surface waters, and to reduce the deposition to terrestrial natural ecosystems. However, there is still a major challenge in complying with the EU Water Framework and Habitats Directives, calling for new approaches, measures and technologies to mitigate agricultural N losses and control N flows.